Signature forgery detection device

Abstract

A method and apparatus for handwriting analysis wherein a signature or other writing can be subjected to comparison with a reference signature. The apparatus and method rely on the collection of measurements of the optical density of a plurality of elements in the specimen and selectively retaining said measurements and then comparing each density measurement to a threshold value. Ultimately, only those density measurements are retained which are located within a bounded locus. After the retained density measurements have been established, they are automatically compared to the measurements of the specimen signature to permit the apparatus to accept or reject the signature on the presented document.

We claim: 
     
       1. A method for analyzing an inscribed specimen comprising the steps of: (a) collecting measurements of the optical density of a plurality of elements in the specimen across the grey scale;   (b) selectively retaining a plurality of the density measurements;   (c) processing the retained measurements by comparing each density measurement to a threshold value;   (d) conditionally retaining each density measurement with reference to the threshold value;   (e) forming a bounded locus of density measurements spatially distributed about each density measurement to be tested for retention;   (f) retaining only those conditionally retained density measurements which are members of a set of conditionally retained density measurements including at least one density measurement of an element conditionally retained within the locus;   (g) assigning retained density measurements to line segments;   (h) determining the location of said segments;   (i) forming vectors by combining measurements of said measurements within each line segment; and   (j) comparing the vectors to the vectors of a stored representation of a reference specimen.   
     
     
       2. The method of claim 1 wherein the stored representation of a reference specimen is obtained by analysis of the optical density variations of the reference specimen. 
     
     
       3. A device for analyzing an inscribed specimen including: (a) means for collecting measurements of the optical density of a plurality of specimen elements across the grey scale, said means for collecting density measurements comprising remote optical scanning means which optically measure the light from each element of the specimen and transmits to a central processing unit;   (b) storage means for retaining a plurality of said density measurements;   (c) means for processing said retained measurements;   (d) means for reporting the results of said processing;   (e) comparison means for comparing each measurement to a threshold value;   (f) control means for conditionally retaining each measurement which discriminates from the threshold value and for forming a bounded locus of measurements spatially distributed about each measurement to be tested for retention, and for retaining only those conditionally retained measurements which are members of a set of conditionally retained measurements including at least a measurement within the locus; and   (g) processing means for the retained measurements comprising means for converting said retained measurements to line segments, for determining the location of the segments, for forming vectors by combining said measurements within each line segment, and for comparing the vectors to the vectors of a stored representation of a reference specimen.   
     
     
       4. The device of claim 3 which includes reference input means whereby the stored vectors of a reference specimen is received by the device for comparison.